1. Field of the Invention
The present invention relates to an organic light emitting display and, more particularly, to an organic light emitting display in an active matrix.
2. Description of the Related Art
An organic light emitting display includes organic light emitting diodes, each having an anode electrode, an organic light emitting layer, and a cathode electrode. The organic light emitting display is divided into a passive matrix organic light emitting display in which organic light emitting diodes are coupled between scan lines and data lines in a matrix to form pixels, and an active matrix organic light emitting diode in which the operations of pixels are controlled by thin film transistors (TFTs) that function as switches. In general, the active matrix organic light emitting display includes TFTs for transmitting signals and capacitors for maintaining signals.
Since organic light emitting displays may be manufactured to be light and thin, the applications of the organic light emitting displays to portable displays increase. Recently, in accordance with the requests of users, the resolutions of the organic light emitting displays have increased and the sizes of the organic light emitting displays have been reduced.
When the resolution increases, due to reduction in the size of the pixels, the size of a light emitting region which transmits light (that is, an aperture ratio) is reduced. Due to reduction in brightness caused by reduction in the aperture ratio, picture quality deteriorates.
Furthermore, as a method of reducing manufacturing cost, research on reducing the number of masks has been continuously performed. Since the TFTs and the capacitors do not overlap in order to minimize the number of masks, the size of the pixels is limited. In addition, due to reduction in the size of the capacitors in accordance with reduction in the size of the pixels, it is difficult to secure the necessary capacitance.